1. Field of the Invention
This invention relates to an image processing method and apparatus, in which a direction transforming process for reversing and/or rotating an image signal representing an image of an object is performed in accordance with information giving specifics about an image recording technique, such as the direction from which the image of the object, e.g. a patient, is recorded, and the orientation of the object in the image recording operation. This invention also relates to a recording medium, on which a program for causing a computer to execute the image processing method has been recorded and from which the computer is capable of reading the program.
2. Description of the Prior Art
It has been proposed by the applicant to use stimulable phosphors in radiation image recording and reproducing systems. Specifically, a radiation image of an object, such as a human body, is recorded on a sheet provided with a layer of the stimulable phosphor (hereinafter referred to as a stimulable phosphor sheet). The stimulable phosphor sheet, on which the radiation image has been stored, is then exposed to stimulating rays, such as a laser beam, which cause it to emit light in proportion to the amount of energy stored thereon during its exposure to the radiation. The light emitted by the stimulable phosphor sheet, upon stimulation thereof, is photoelectrically detected and converted into an electric image signal. The image signal is then subjected to image processing, such as gradation processing, and the thus obtained processed image signal is used for the reproduction of the radiation image of the object as a visible image on a recording material.
In the radiation image recording and reproducing systems described above, the operation for recording a radiation image of an object is performed with one of various image recording techniques. For example, in cases where a radiation image of the chest of a patient is to be recorded, radiation may be irradiated to the patient from the back side of the patient or from the abdomen side of the patient. Also, in the image recording operation, the patient may stand facing the stimulable phosphor sheet or may stand facing the side opposite to the stimulable phosphor sheet. The image signal having been obtained by reading out the recorded radiation image is subjected to a process for reversing or rotating the radiation image in accordance with the image recording technique, which was employed in the image recording operation, and the image signal having been obtained from the process is utilized for reproducing the radiation image as a visible image. By way of example, in cases where the image recording operation is performed, in which the patient stands facing the stimulable phosphor sheet and radiation is irradiated to the patient from the back side of the patient, the radiation image shown in FIG. 2A is obtained, in which a pattern of the heart is embedded on the left side when the radiation image is seen from the direction of irradiation of the radiation. However, when the radiation image is to be used for making a diagnosis of an illness, it is necessary that the heart pattern is located on the right side as the person, who sees the image, stands facing the image. Therefore, in such cases, as illustrated in FIG. 2B, a process for reversing the right and left sides of the image represented by the original image signal is performed on the original image signal, and a reversed image signal is thereby obtained. The reversed image signal is then utilized for reproducing a visible image. In this manner, a reproduced image, in which the heart pattern is located on the right side as the person, who sees the image, stands facing the image, can be obtained.
An operation for recording a radiation image of an object is often performed by the utilization of a marker for representing the direction from which the image of the object is recorded, the orientation of the object, e.g. a patient, in the image recording operation, or the like. The marker utilized in the image recording operation is formed from a metal, such as lead, which does not transmit radiation. For example, in cases where a radiation image of the chest of a human body is to be obtained, an L-shaped marker may be attached to an upper left corner area of the stimulable phosphor sheet, and the image pattern of the marker may be recorded together with the object image on the stimulable phosphor sheet. In such cases, the radiation image shown in FIG. 3A is obtained, in which the L-shaped marker pattern is embedded at the upper left corner area when the radiation image is seen from the direction of irradiation of the radiation. When the radiation image shown in FIG. 3A is reproduced as a visible image, the right and left sides of the image represented by the original image signal are reversed, and the image shown in FIG. 3B is obtained. In such cases, when a person sees the reproduced image, since the L-shaped marker pattern has been reversed, the person can easily recognize that the right and left sides of the image have been reversed.
Instead of the marker pattern being recorded together with the object image, it may be considered to append a digital marker signal representing the marker pattern to the image signal representing the radiation image. In cases where the marker signal is thus appended to the image signal, a radiation image can be obtained, in which the marker pattern has been appended to a desired position. Also, a marker pattern having an arbitrary shape can be embedded in the radiation image.
However, as described above, the image signal, to which the marker signal is to be appended, is often subjected to the direction transforming process through reversion or rotation in accordance with the information giving specifics about the image recording technique. Therefore, if the marker signal is directly appended to the image signal, which has been obtained from the direction transforming process, the problems described below will occur. Specifically, the problems will occur in that, for example, as illustrated in FIG. 19, in cases where the marker signal is the one representing the L-shaped marker pattern, the image represented by the image signal has been transformed in direction, but the L-shaped marker pattern is appended to the image in the form having not been transformed in direction. Therefore, the person, who sees the radiation image, will misunderstand that the radiation image is the one having not been transformed in direction, and there is the risk that an incorrect diagnosis, or the like, will be made.